China: time zone history, and your birth hour
The clocks in China have changed 29 times since 1900. Today they run on UTC+8; the last change was on 15 Sep 1991. A calculator that uses today’s offset for every birth is out by some minutes for anyone born in any of the different eras below.
Since 1925, the widest gap is the summer time from 1919: 60 minutes, enough to move about 50% of births into a different two-hour period.
Every era
| From – to | Clock | Versus today · births in another hour |
|---|---|---|
| 1 Jan 1900 – 31 Dec 1900 | UTC+8:06 local mean time | +6 min about 5% |
| 31 Dec 1900 – 13 Apr 1919 | UTC+8 standard time | same |
1919–1991, 14 stretcheseach stretch
| UTC+9 in summer, UTC+8 the rest of the year | up to 60 min about 50% |
| 15 Sep 1991 – today | UTC+8 standard time | same |
The second figure in each row is the births moved into another two-hour period: about m/120 of them when the clock is m minutes out. For Kuala Lumpur, 30 minutes out from 1946 to 1981, the measured share is 26.0% of 4,000 sampled births.
Born in summer time?
In each of these, the clocks ran ahead of standard time. A birth inside one happened that much earlier by the sun than the clock said; give the birthplace and this site’s calculator takes it off for you.
- From 4 May 1986, 02:00 to 14 Sep 1986, 02:00 · 60 minutes ahead
- From 12 Apr 1987, 02:00 to 13 Sep 1987, 02:00 · 60 minutes ahead
- From 17 Apr 1988, 02:00 to 11 Sep 1988, 02:00 · 60 minutes ahead
- From 16 Apr 1989, 02:00 to 17 Sep 1989, 02:00 · 60 minutes ahead
- From 15 Apr 1990, 02:00 to 16 Sep 1990, 02:00 · 60 minutes ahead
- From 14 Apr 1991, 02:00 to 15 Sep 1991, 02:00 · 60 minutes ahead
Times are on the local clock: when each began the clocks went forward, and when it ended they went back.
What the database does not record
Two things the database does not record, and this page does not guess. Before 1949 China was divided on paper into five time zones (proposed in 1918, put officially in place in March 1948): Kunlun UTC+5:30, Xinjiang–Tibet UTC+6, Long-Shu UTC+7 (Sichuan, Yunnan, Guizhou, Guangxi, Shaanxi and others), Zhongyuan UTC+8 (most of China) and Changbai UTC+8:30 (Heilongjiang, Jilin). In practice they were observed mainly on the coast, and the database keeps only Shanghai’s clock; Japanese-occupied Manchuria ran on Tokyo time, UTC+9. For a birth before 1949 away from the coast, the clock in use is uncertain, and so is the hour. Xinjiang keeps two clocks in daily use, Beijing time and Xinjiang time (UTC+6), and a recorded birth time could be on either, so Xinjiang’s cities are not in this site’s list.
Source: the notes in the IANA time zone database’s asia file.